1. Field of the Invention
This invention relates to a ceramic multilayer wiring board.
2. Description of the Prior Art
Generally, ceramic multilayer wiring boards are provided with through-holes filled with a conductor for connecting the multilayer wiring patterns to each other. In conventional ceramic multilayer wiring boards, as illustrated in FIG. 1 of the drawings attached hereto, the diameter of each through-hole 3 filled with a conductor 2 was same in both the surface and inside layers of the board 1. The same thing is seen in the device of U.S. Pat. No. 4,345,955.
Such conventional ceramic multilayer wiring boards were liable to suffer from cracks 4 around the conductor-filled through-holes 3 as shown in FIG. 2 because of the greater coefficient of thermal expansion of the ceramic material used for the substrate than that of the conductor in the through-holes.